projects/linux·blob v3.13 · refs

769 lines · 19.8 KiB

1/*
2 * Copyright (C) 2008 Mathieu Desnoyers
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 */
18#include <linux/module.h>
19#include <linux/mutex.h>
20#include <linux/types.h>
21#include <linux/jhash.h>
22#include <linux/list.h>
23#include <linux/rcupdate.h>
24#include <linux/tracepoint.h>
25#include <linux/err.h>
26#include <linux/slab.h>
27#include <linux/sched.h>
28#include <linux/static_key.h>
29
30extern struct tracepoint * const __start___tracepoints_ptrs[];
31extern struct tracepoint * const __stop___tracepoints_ptrs[];
32
33/* Set to 1 to enable tracepoint debug output */
34static const int tracepoint_debug;
35
36/*
37 * Tracepoints mutex protects the builtin and module tracepoints and the hash
38 * table, as well as the local module list.
39 */
40static DEFINE_MUTEX(tracepoints_mutex);
41
42#ifdef CONFIG_MODULES
43/* Local list of struct module */
44static LIST_HEAD(tracepoint_module_list);
45#endif /* CONFIG_MODULES */
46
47/*
48 * Tracepoint hash table, containing the active tracepoints.
49 * Protected by tracepoints_mutex.
50 */
51#define TRACEPOINT_HASH_BITS 6
52#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
53static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
54
55/*
56 * Note about RCU :
57 * It is used to delay the free of multiple probes array until a quiescent
58 * state is reached.
59 * Tracepoint entries modifications are protected by the tracepoints_mutex.
60 */
61struct tracepoint_entry {
62 struct hlist_node hlist;
63 struct tracepoint_func *funcs;
64 int refcount; /* Number of times armed. 0 if disarmed. */
65 char name[0];
66};
67
68struct tp_probes {
69 union {
70 struct rcu_head rcu;
71 struct list_head list;
72 } u;
73 struct tracepoint_func probes[0];
74};
75
76static inline void *allocate_probes(int count)
77{
78 struct tp_probes *p = kmalloc(count * sizeof(struct tracepoint_func)
79 + sizeof(struct tp_probes), GFP_KERNEL);
80 return p == NULL ? NULL : p->probes;
81}
82
83static void rcu_free_old_probes(struct rcu_head *head)
84{
85 kfree(container_of(head, struct tp_probes, u.rcu));
86}
87
88static inline void release_probes(struct tracepoint_func *old)
89{
90 if (old) {
91 struct tp_probes *tp_probes = container_of(old,
92 struct tp_probes, probes[0]);
93 call_rcu_sched(&tp_probes->u.rcu, rcu_free_old_probes);
94 }
95}
96
97static void debug_print_probes(struct tracepoint_entry *entry)
98{
99 int i;
100
101 if (!tracepoint_debug || !entry->funcs)
102 return;
103
104 for (i = 0; entry->funcs[i].func; i++)
105 printk(KERN_DEBUG "Probe %d : %p\n", i, entry->funcs[i].func);
106}
107
108static struct tracepoint_func *
109tracepoint_entry_add_probe(struct tracepoint_entry *entry,
110 void *probe, void *data)
111{
112 int nr_probes = 0;
113 struct tracepoint_func *old, *new;
114
115 if (WARN_ON(!probe))
116 return ERR_PTR(-EINVAL);
117
118 debug_print_probes(entry);
119 old = entry->funcs;
120 if (old) {
121 /* (N -> N+1), (N != 0, 1) probes */
122 for (nr_probes = 0; old[nr_probes].func; nr_probes++)
123 if (old[nr_probes].func == probe &&
124 old[nr_probes].data == data)
125 return ERR_PTR(-EEXIST);
126 }
127 /* + 2 : one for new probe, one for NULL func */
128 new = allocate_probes(nr_probes + 2);
129 if (new == NULL)
130 return ERR_PTR(-ENOMEM);
131 if (old)
132 memcpy(new, old, nr_probes * sizeof(struct tracepoint_func));
133 new[nr_probes].func = probe;
134 new[nr_probes].data = data;
135 new[nr_probes + 1].func = NULL;
136 entry->refcount = nr_probes + 1;
137 entry->funcs = new;
138 debug_print_probes(entry);
139 return old;
140}
141
142static void *
143tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
144 void *probe, void *data)
145{
146 int nr_probes = 0, nr_del = 0, i;
147 struct tracepoint_func *old, *new;
148
149 old = entry->funcs;
150
151 if (!old)
152 return ERR_PTR(-ENOENT);
153
154 debug_print_probes(entry);
155 /* (N -> M), (N > 1, M >= 0) probes */
156 if (probe) {
157 for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
158 if (old[nr_probes].func == probe &&
159 old[nr_probes].data == data)
160 nr_del++;
161 }
162 }
163
164 /*
165 * If probe is NULL, then nr_probes = nr_del = 0, and then the
166 * entire entry will be removed.
167 */
168 if (nr_probes - nr_del == 0) {
169 /* N -> 0, (N > 1) */
170 entry->funcs = NULL;
171 entry->refcount = 0;
172 debug_print_probes(entry);
173 return old;
174 } else {
175 int j = 0;
176 /* N -> M, (N > 1, M > 0) */
177 /* + 1 for NULL */
178 new = allocate_probes(nr_probes - nr_del + 1);
179 if (new == NULL)
180 return ERR_PTR(-ENOMEM);
181 for (i = 0; old[i].func; i++)
182 if (old[i].func != probe || old[i].data != data)
183 new[j++] = old[i];
184 new[nr_probes - nr_del].func = NULL;
185 entry->refcount = nr_probes - nr_del;
186 entry->funcs = new;
187 }
188 debug_print_probes(entry);
189 return old;
190}
191
192/*
193 * Get tracepoint if the tracepoint is present in the tracepoint hash table.
194 * Must be called with tracepoints_mutex held.
195 * Returns NULL if not present.
196 */
197static struct tracepoint_entry *get_tracepoint(const char *name)
198{
199 struct hlist_head *head;
200 struct tracepoint_entry *e;
201 u32 hash = jhash(name, strlen(name), 0);
202
203 head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
204 hlist_for_each_entry(e, head, hlist) {
205 if (!strcmp(name, e->name))
206 return e;
207 }
208 return NULL;
209}
210
211/*
212 * Add the tracepoint to the tracepoint hash table. Must be called with
213 * tracepoints_mutex held.
214 */
215static struct tracepoint_entry *add_tracepoint(const char *name)
216{
217 struct hlist_head *head;
218 struct tracepoint_entry *e;
219 size_t name_len = strlen(name) + 1;
220 u32 hash = jhash(name, name_len-1, 0);
221
222 head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
223 hlist_for_each_entry(e, head, hlist) {
224 if (!strcmp(name, e->name)) {
225 printk(KERN_NOTICE
226 "tracepoint %s busy\n", name);
227 return ERR_PTR(-EEXIST); /* Already there */
228 }
229 }
230 /*
231 * Using kmalloc here to allocate a variable length element. Could
232 * cause some memory fragmentation if overused.
233 */
234 e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL);
235 if (!e)
236 return ERR_PTR(-ENOMEM);
237 memcpy(&e->name[0], name, name_len);
238 e->funcs = NULL;
239 e->refcount = 0;
240 hlist_add_head(&e->hlist, head);
241 return e;
242}
243
244/*
245 * Remove the tracepoint from the tracepoint hash table. Must be called with
246 * mutex_lock held.
247 */
248static inline void remove_tracepoint(struct tracepoint_entry *e)
249{
250 hlist_del(&e->hlist);
251 kfree(e);
252}
253
254/*
255 * Sets the probe callback corresponding to one tracepoint.
256 */
257static void set_tracepoint(struct tracepoint_entry **entry,
258 struct tracepoint *elem, int active)
259{
260 WARN_ON(strcmp((*entry)->name, elem->name) != 0);
261
262 if (elem->regfunc && !static_key_enabled(&elem->key) && active)
263 elem->regfunc();
264 else if (elem->unregfunc && static_key_enabled(&elem->key) && !active)
265 elem->unregfunc();
266
267 /*
268 * rcu_assign_pointer has a smp_wmb() which makes sure that the new
269 * probe callbacks array is consistent before setting a pointer to it.
270 * This array is referenced by __DO_TRACE from
271 * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
272 * is used.
273 */
274 rcu_assign_pointer(elem->funcs, (*entry)->funcs);
275 if (active && !static_key_enabled(&elem->key))
276 static_key_slow_inc(&elem->key);
277 else if (!active && static_key_enabled(&elem->key))
278 static_key_slow_dec(&elem->key);
279}
280
281/*
282 * Disable a tracepoint and its probe callback.
283 * Note: only waiting an RCU period after setting elem->call to the empty
284 * function insures that the original callback is not used anymore. This insured
285 * by preempt_disable around the call site.
286 */
287static void disable_tracepoint(struct tracepoint *elem)
288{
289 if (elem->unregfunc && static_key_enabled(&elem->key))
290 elem->unregfunc();
291
292 if (static_key_enabled(&elem->key))
293 static_key_slow_dec(&elem->key);
294 rcu_assign_pointer(elem->funcs, NULL);
295}
296
297/**
298 * tracepoint_update_probe_range - Update a probe range
299 * @begin: beginning of the range
300 * @end: end of the range
301 *
302 * Updates the probe callback corresponding to a range of tracepoints.
303 * Called with tracepoints_mutex held.
304 */
305static void tracepoint_update_probe_range(struct tracepoint * const *begin,
306 struct tracepoint * const *end)
307{
308 struct tracepoint * const *iter;
309 struct tracepoint_entry *mark_entry;
310
311 if (!begin)
312 return;
313
314 for (iter = begin; iter < end; iter++) {
315 mark_entry = get_tracepoint((*iter)->name);
316 if (mark_entry) {
317 set_tracepoint(&mark_entry, *iter,
318 !!mark_entry->refcount);
319 } else {
320 disable_tracepoint(*iter);
321 }
322 }
323}
324
325#ifdef CONFIG_MODULES
326void module_update_tracepoints(void)
327{
328 struct tp_module *tp_mod;
329
330 list_for_each_entry(tp_mod, &tracepoint_module_list, list)
331 tracepoint_update_probe_range(tp_mod->tracepoints_ptrs,
332 tp_mod->tracepoints_ptrs + tp_mod->num_tracepoints);
333}
334#else /* CONFIG_MODULES */
335void module_update_tracepoints(void)
336{
337}
338#endif /* CONFIG_MODULES */
339
340
341/*
342 * Update probes, removing the faulty probes.
343 * Called with tracepoints_mutex held.
344 */
345static void tracepoint_update_probes(void)
346{
347 /* Core kernel tracepoints */
348 tracepoint_update_probe_range(__start___tracepoints_ptrs,
349 __stop___tracepoints_ptrs);
350 /* tracepoints in modules. */
351 module_update_tracepoints();
352}
353
354static struct tracepoint_func *
355tracepoint_add_probe(const char *name, void *probe, void *data)
356{
357 struct tracepoint_entry *entry;
358 struct tracepoint_func *old;
359
360 entry = get_tracepoint(name);
361 if (!entry) {
362 entry = add_tracepoint(name);
363 if (IS_ERR(entry))
364 return (struct tracepoint_func *)entry;
365 }
366 old = tracepoint_entry_add_probe(entry, probe, data);
367 if (IS_ERR(old) && !entry->refcount)
368 remove_tracepoint(entry);
369 return old;
370}
371
372/**
373 * tracepoint_probe_register - Connect a probe to a tracepoint
374 * @name: tracepoint name
375 * @probe: probe handler
376 *
377 * Returns 0 if ok, error value on error.
378 * The probe address must at least be aligned on the architecture pointer size.
379 */
380int tracepoint_probe_register(const char *name, void *probe, void *data)
381{
382 struct tracepoint_func *old;
383
384 mutex_lock(&tracepoints_mutex);
385 old = tracepoint_add_probe(name, probe, data);
386 if (IS_ERR(old)) {
387 mutex_unlock(&tracepoints_mutex);
388 return PTR_ERR(old);
389 }
390 tracepoint_update_probes(); /* may update entry */
391 mutex_unlock(&tracepoints_mutex);
392 release_probes(old);
393 return 0;
394}
395EXPORT_SYMBOL_GPL(tracepoint_probe_register);
396
397static struct tracepoint_func *
398tracepoint_remove_probe(const char *name, void *probe, void *data)
399{
400 struct tracepoint_entry *entry;
401 struct tracepoint_func *old;
402
403 entry = get_tracepoint(name);
404 if (!entry)
405 return ERR_PTR(-ENOENT);
406 old = tracepoint_entry_remove_probe(entry, probe, data);
407 if (IS_ERR(old))
408 return old;
409 if (!entry->refcount)
410 remove_tracepoint(entry);
411 return old;
412}
413
414/**
415 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
416 * @name: tracepoint name
417 * @probe: probe function pointer
418 *
419 * We do not need to call a synchronize_sched to make sure the probes have
420 * finished running before doing a module unload, because the module unload
421 * itself uses stop_machine(), which insures that every preempt disabled section
422 * have finished.
423 */
424int tracepoint_probe_unregister(const char *name, void *probe, void *data)
425{
426 struct tracepoint_func *old;
427
428 mutex_lock(&tracepoints_mutex);
429 old = tracepoint_remove_probe(name, probe, data);
430 if (IS_ERR(old)) {
431 mutex_unlock(&tracepoints_mutex);
432 return PTR_ERR(old);
433 }
434 tracepoint_update_probes(); /* may update entry */
435 mutex_unlock(&tracepoints_mutex);
436 release_probes(old);
437 return 0;
438}
439EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
440
441static LIST_HEAD(old_probes);
442static int need_update;
443
444static void tracepoint_add_old_probes(void *old)
445{
446 need_update = 1;
447 if (old) {
448 struct tp_probes *tp_probes = container_of(old,
449 struct tp_probes, probes[0]);
450 list_add(&tp_probes->u.list, &old_probes);
451 }
452}
453
454/**
455 * tracepoint_probe_register_noupdate - register a probe but not connect
456 * @name: tracepoint name
457 * @probe: probe handler
458 *
459 * caller must call tracepoint_probe_update_all()
460 */
461int tracepoint_probe_register_noupdate(const char *name, void *probe,
462 void *data)
463{
464 struct tracepoint_func *old;
465
466 mutex_lock(&tracepoints_mutex);
467 old = tracepoint_add_probe(name, probe, data);
468 if (IS_ERR(old)) {
469 mutex_unlock(&tracepoints_mutex);
470 return PTR_ERR(old);
471 }
472 tracepoint_add_old_probes(old);
473 mutex_unlock(&tracepoints_mutex);
474 return 0;
475}
476EXPORT_SYMBOL_GPL(tracepoint_probe_register_noupdate);
477
478/**
479 * tracepoint_probe_unregister_noupdate - remove a probe but not disconnect
480 * @name: tracepoint name
481 * @probe: probe function pointer
482 *
483 * caller must call tracepoint_probe_update_all()
484 */
485int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
486 void *data)
487{
488 struct tracepoint_func *old;
489
490 mutex_lock(&tracepoints_mutex);
491 old = tracepoint_remove_probe(name, probe, data);
492 if (IS_ERR(old)) {
493 mutex_unlock(&tracepoints_mutex);
494 return PTR_ERR(old);
495 }
496 tracepoint_add_old_probes(old);
497 mutex_unlock(&tracepoints_mutex);
498 return 0;
499}
500EXPORT_SYMBOL_GPL(tracepoint_probe_unregister_noupdate);
501
502/**
503 * tracepoint_probe_update_all - update tracepoints
504 */
505void tracepoint_probe_update_all(void)
506{
507 LIST_HEAD(release_probes);
508 struct tp_probes *pos, *next;
509
510 mutex_lock(&tracepoints_mutex);
511 if (!need_update) {
512 mutex_unlock(&tracepoints_mutex);
513 return;
514 }
515 if (!list_empty(&old_probes))
516 list_replace_init(&old_probes, &release_probes);
517 need_update = 0;
518 tracepoint_update_probes();
519 mutex_unlock(&tracepoints_mutex);
520 list_for_each_entry_safe(pos, next, &release_probes, u.list) {
521 list_del(&pos->u.list);
522 call_rcu_sched(&pos->u.rcu, rcu_free_old_probes);
523 }
524}
525EXPORT_SYMBOL_GPL(tracepoint_probe_update_all);
526
527/**
528 * tracepoint_get_iter_range - Get a next tracepoint iterator given a range.
529 * @tracepoint: current tracepoints (in), next tracepoint (out)
530 * @begin: beginning of the range
531 * @end: end of the range
532 *
533 * Returns whether a next tracepoint has been found (1) or not (0).
534 * Will return the first tracepoint in the range if the input tracepoint is
535 * NULL.
536 */
537static int tracepoint_get_iter_range(struct tracepoint * const **tracepoint,
538 struct tracepoint * const *begin, struct tracepoint * const *end)
539{
540 if (!*tracepoint && begin != end) {
541 *tracepoint = begin;
542 return 1;
543 }
544 if (*tracepoint >= begin && *tracepoint < end)
545 return 1;
546 return 0;
547}
548
549#ifdef CONFIG_MODULES
550static void tracepoint_get_iter(struct tracepoint_iter *iter)
551{
552 int found = 0;
553 struct tp_module *iter_mod;
554
555 /* Core kernel tracepoints */
556 if (!iter->module) {
557 found = tracepoint_get_iter_range(&iter->tracepoint,
558 __start___tracepoints_ptrs,
559 __stop___tracepoints_ptrs);
560 if (found)
561 goto end;
562 }
563 /* Tracepoints in modules */
564 mutex_lock(&tracepoints_mutex);
565 list_for_each_entry(iter_mod, &tracepoint_module_list, list) {
566 /*
567 * Sorted module list
568 */
569 if (iter_mod < iter->module)
570 continue;
571 else if (iter_mod > iter->module)
572 iter->tracepoint = NULL;
573 found = tracepoint_get_iter_range(&iter->tracepoint,
574 iter_mod->tracepoints_ptrs,
575 iter_mod->tracepoints_ptrs
576 + iter_mod->num_tracepoints);
577 if (found) {
578 iter->module = iter_mod;
579 break;
580 }
581 }
582 mutex_unlock(&tracepoints_mutex);
583end:
584 if (!found)
585 tracepoint_iter_reset(iter);
586}
587#else /* CONFIG_MODULES */
588static void tracepoint_get_iter(struct tracepoint_iter *iter)
589{
590 int found = 0;
591
592 /* Core kernel tracepoints */
593 found = tracepoint_get_iter_range(&iter->tracepoint,
594 __start___tracepoints_ptrs,
595 __stop___tracepoints_ptrs);
596 if (!found)
597 tracepoint_iter_reset(iter);
598}
599#endif /* CONFIG_MODULES */
600
601void tracepoint_iter_start(struct tracepoint_iter *iter)
602{
603 tracepoint_get_iter(iter);
604}
605EXPORT_SYMBOL_GPL(tracepoint_iter_start);
606
607void tracepoint_iter_next(struct tracepoint_iter *iter)
608{
609 iter->tracepoint++;
610 /*
611 * iter->tracepoint may be invalid because we blindly incremented it.
612 * Make sure it is valid by marshalling on the tracepoints, getting the
613 * tracepoints from following modules if necessary.
614 */
615 tracepoint_get_iter(iter);
616}
617EXPORT_SYMBOL_GPL(tracepoint_iter_next);
618
619void tracepoint_iter_stop(struct tracepoint_iter *iter)
620{
621}
622EXPORT_SYMBOL_GPL(tracepoint_iter_stop);
623
624void tracepoint_iter_reset(struct tracepoint_iter *iter)
625{
626#ifdef CONFIG_MODULES
627 iter->module = NULL;
628#endif /* CONFIG_MODULES */
629 iter->tracepoint = NULL;
630}
631EXPORT_SYMBOL_GPL(tracepoint_iter_reset);
632
633#ifdef CONFIG_MODULES
634static int tracepoint_module_coming(struct module *mod)
635{
636 struct tp_module *tp_mod, *iter;
637 int ret = 0;
638
639 /*
640 * We skip modules that taint the kernel, especially those with different
641 * module headers (for forced load), to make sure we don't cause a crash.
642 * Staging and out-of-tree GPL modules are fine.
643 */
644 if (mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP)))
645 return 0;
646 mutex_lock(&tracepoints_mutex);
647 tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
648 if (!tp_mod) {
649 ret = -ENOMEM;
650 goto end;
651 }
652 tp_mod->num_tracepoints = mod->num_tracepoints;
653 tp_mod->tracepoints_ptrs = mod->tracepoints_ptrs;
654
655 /*
656 * tracepoint_module_list is kept sorted by struct module pointer
657 * address for iteration on tracepoints from a seq_file that can release
658 * the mutex between calls.
659 */
660 list_for_each_entry_reverse(iter, &tracepoint_module_list, list) {
661 BUG_ON(iter == tp_mod); /* Should never be in the list twice */
662 if (iter < tp_mod) {
663 /* We belong to the location right after iter. */
664 list_add(&tp_mod->list, &iter->list);
665 goto module_added;
666 }
667 }
668 /* We belong to the beginning of the list */
669 list_add(&tp_mod->list, &tracepoint_module_list);
670module_added:
671 tracepoint_update_probe_range(mod->tracepoints_ptrs,
672 mod->tracepoints_ptrs + mod->num_tracepoints);
673end:
674 mutex_unlock(&tracepoints_mutex);
675 return ret;
676}
677
678static int tracepoint_module_going(struct module *mod)
679{
680 struct tp_module *pos;
681
682 mutex_lock(&tracepoints_mutex);
683 tracepoint_update_probe_range(mod->tracepoints_ptrs,
684 mod->tracepoints_ptrs + mod->num_tracepoints);
685 list_for_each_entry(pos, &tracepoint_module_list, list) {
686 if (pos->tracepoints_ptrs == mod->tracepoints_ptrs) {
687 list_del(&pos->list);
688 kfree(pos);
689 break;
690 }
691 }
692 /*
693 * In the case of modules that were tainted at "coming", we'll simply
694 * walk through the list without finding it. We cannot use the "tainted"
695 * flag on "going", in case a module taints the kernel only after being
696 * loaded.
697 */
698 mutex_unlock(&tracepoints_mutex);
699 return 0;
700}
701
702int tracepoint_module_notify(struct notifier_block *self,
703 unsigned long val, void *data)
704{
705 struct module *mod = data;
706 int ret = 0;
707
708 switch (val) {
709 case MODULE_STATE_COMING:
710 ret = tracepoint_module_coming(mod);
711 break;
712 case MODULE_STATE_LIVE:
713 break;
714 case MODULE_STATE_GOING:
715 ret = tracepoint_module_going(mod);
716 break;
717 }
718 return ret;
719}
720
721struct notifier_block tracepoint_module_nb = {
722 .notifier_call = tracepoint_module_notify,
723 .priority = 0,
724};
725
726static int init_tracepoints(void)
727{
728 return register_module_notifier(&tracepoint_module_nb);
729}
730__initcall(init_tracepoints);
731#endif /* CONFIG_MODULES */
732
733#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
734
735/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
736static int sys_tracepoint_refcount;
737
738void syscall_regfunc(void)
739{
740 unsigned long flags;
741 struct task_struct *g, *t;
742
743 if (!sys_tracepoint_refcount) {
744 read_lock_irqsave(&tasklist_lock, flags);
745 do_each_thread(g, t) {
746 /* Skip kernel threads. */
747 if (t->mm)
748 set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
749 } while_each_thread(g, t);
750 read_unlock_irqrestore(&tasklist_lock, flags);
751 }
752 sys_tracepoint_refcount++;
753}
754
755void syscall_unregfunc(void)
756{
757 unsigned long flags;
758 struct task_struct *g, *t;
759
760 sys_tracepoint_refcount--;
761 if (!sys_tracepoint_refcount) {
762 read_lock_irqsave(&tasklist_lock, flags);
763 do_each_thread(g, t) {
764 clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
765 } while_each_thread(g, t);
766 read_unlock_irqrestore(&tasklist_lock, flags);
767 }
768}
769#endif